1. Field of the Invention
The present invention relates to the creating of a desired light dispersion pattern using light transmitted from a remote source by fiber optics. More particularly, the present invention relates to a novel light head assembly for dispersing light generated by a remote light source, especially a high intensity discharge (HID) source, and transmitted to the light head assembly through one or more optical fibers. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Related Art
Attempts to achieve area illumination using light generated by a remotely located light source and transmitted to a light head assembly via fiber optics are known in the art. However, to date, most light head assemblies designed for use with remote light sources have been mere variations on a single basic design configuration. This basic configuration employs a symmetric concave housing having an aperture within a central region thereof and a light transmissive lens which cooperates with the concave housing to define a chamber therebetween. An optical fiber or bundle of fibers, commonly known as a light pipe, extends from the remote light source to the light head and transmits the light generated by the remote source to the light head housing. The light pipe projects through the aperture in the light head housing in a direction which is parallel to the axis of symmetry of the housing and terminates within the chamber of the housing. Since the intensity of the light emitted from the end of a light pipe decreases rapidly as the viewer moves off-axis, and the light emitting end of a light pipe is effectively a very small diameter light source, the prior art employs a lens with a complex pattern of light refracting elements in an attempt to achieve a desired pattern of dispersion of light passing through the lens into the ambient environment.
The use of a light pipe as the light source in a head assembly offers a number of advantages over light head assemblies employing conventional "point" light sources, such as gaseous discharge tubes or high intensity incandescent lamps. Among these advantages are the absence of high temperatures and the elimination of the possibility of electric sparks within the light head assembly. The absence of high temperatures within the light head assembly allows the components of the light head to be fabricated from comparatively inexpensive low temperature plastic materials.
However, despite the significant potential benefits offered by light head assemblies designed for use with fiber optic cables and remotely located light sources, such assemblies have not found widespread utility due to a number of inherent deficiencies. The principal deficiency, as noted above, arises from the fact that a light pipe defines a very small area light source and the intensity of that source decreases rapidly off-axis. For example, in one commercially available optical fiber, approximately ninety (90%) percent of the available light may be measured within twenty five (25%) degrees of the axis of the light pipe. Thus, the area illuminated by a closely spaced light pipe is far too small in cross-section to serve as a spot or warning light. Accordingly, light head assemblies which employ a light pipe as the source of light must employ some means of improving light dispersion.
Previous attempts to control the dispersion of light emanating from a light pipe have resulted in light head assemblies with several deficiencies. As a first deficiency, previously available light head assemblies of this nature have employed relatively complex lenses to refract the light emitted from the end of the light pipe. In addition to being expensive, the use of such a lens results in a comparatively high degree of attenuation. A second deficiency of previously available light head assemblies which receive light from an associated light pipe resides in their elongated shape, i.e., their depth in the direction of travel of the light rays. Thus, in an effort to increase the area illuminated, previously available light head assemblies have spaced the emitting end of the light pipe a substantial distance from the refracting lens. While such spacing improves light dispersion, it also results in a volumetrically inefficient device. Light head assemblies employing such elongated housings are impractical for flush mounting on walls or for use where the space behind the supporting wall is severely limited such as, for example, in the case of a dome light in a vehicle. This problem is exacerbated because these light head assemblies receive the light pipe from the rear of the assembly such that the axis thereof, and thus the axis of the emitted light beam, is oriented substantially parallel to the elongated dimension of the light head housing. Since the relatively fragile nature of optical fibers dictates that the light pipe be routed to prevent tight bends, substantial additional depth is required to mount these light head assemblies to a mounting structure. Thus, light head assemblies which employ a light pipe as the light source have found application in a very limited number of environments.